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Indane and isoindoline are attractive bicyclic systems in biologically active compounds but are rarely reported in DNA-encoded libraries. In this paper, we reported an efficient and versatile approach for assembling indane and isoindoline scaffolds via a ruthenium-catalyzed [2 + 2 + 2] cyclotrimerization reaction. This method exhibits a broad substrate scope and has been successfully applied to construct a 53K-membered DNA-encoded library (DEL). In order to test its application, we carried out a preliminary selection of this DEL against Aurora A protein and identified a hit compound with 9.3 μM inhibition activity.

The photocatalyst-free electron donor-acceptor (EDA) complex photochemistry was deemed to expand the potential of photodriven radical chemistry. Here, we report a cross-coupling reaction of thianthrenium salt functionalized arenes and sodium sulfinates via a photopromoted single electron transfer (SET) process of an EDA complex. A series of biarylsulfones were obtained with high site-selectivity and reactivity. This mild and practical radical reaction could be applied on the bioactive and DNA-encoded molecules.

DNA-encoded library (DEL) technology is a powerful tool in the discovery of bioactive probe molecules and drug leads. Mostly, the success in DEL technology stems from the molecular diversity of the chemical libraries. However, the construction of DELs has been restricted by the idiosyncratic needs and the required low concentration (∼1 mM or less) of the library intermediate. Here, we report visible-light-promoted on-DNA radical coupling reactions via an electron donor-acceptor (EDA) complex and a reversible adsorption to solid support (RASS) strategy. This protocol provides a unique solution to the challenges of increasing the reactivity of highly diluted DNA substrates and reducing the residues of heavy metals from photocatalysts. A series of on-DNA indole sulfone and selenide derivatives were obtained with good to quantitative conversions. It is anticipated that these mild-condition on-DNA radical reactions will significantly improve the chemical diversity of DELs and find widespread utility to DEL construction.

Taking advantage of the diversity-oriented synthesis strategy with α,β-unsaturated carbonyl compounds, we have successfully established the DNA-compatible transformations for various heterocyclic scaffolds. The ring-closure reactions for pyrrole, pyrrolidine, pyrazole, pyrazoline, isoxazoline, pyridine, piperidine, cyclohexenone, and 5,8-dihydroimidazo[1,2-a]pyrimidine were elegantly demonstrated in a DNA-compatible format. These efforts paved the way for preparing DNA-encoded libraries with more extensive chemical space.

To expand the chemical space of DNA-encoded library (DEL) technology, we have developed the DNA-compatible cross-dehydrogenative coupling reaction between tetrahydroisoquinolines (THIQs) and a series of nucleophiles such as nitromethane, terminal alkynes, and so on. Both photo- and metal-promoted conditions have been successfully established for this C-1 derivation of THIQs, as exemplified by the addition of nitromethane. All of these new DNA-compatible transformations have paved the way for the divergent oriented synthesis of THIQ-focused DELs.